1. Field of the Invention
The invention relates to improvements in fluid ram pumps.
2. Description of the Prior Art
In fluid mechanics, it is generally known that an abrupt stop in fluid flow through a pipe will rapidly generate a back pressure of magnitude many times that generated by the dynamic flow. Many people have experienced this phenomenon in their domestic water systems when they quickly shut off a water valve. This phenomenon is commonly known as "water hammer".
In the past, attempts have been made to harness the back pressure to perform useful work, such as vertically pumping high pressure fluid. These pumps are known as ram pumps.
Past designs of ram pumps have had a pump housing or body containing gas, such as air, and having an inlet connnected by a lead or head pipe to a source of flowing fluid, such as a water reservoir located at some height above the pump. Water flows under the influence of gravity from the reservoir through the lead pipe, the pump inlet and in turn into the housing. The housing also has a release valve for water exhaust from the pump; rapid, abrupt closure of that valve creates a pressure increase in the pump housing which compresses air trapped in the housing. In theory, the housing pressure increase opens a lift valve, which allows the compressed air to expand and push water output through the lift valve and out of the pump. The output has a pressure greater than the hydrostatic pressure generated by the dynamic head flowing through the pump and can be used to perform useful mechanical work, such as pressurizing a municipal water system. Also in theory, repeated opening and closing of the release valve repetitively recreates back pressure waves which in turn activate the lift valve and perform useful work.
Ram pumps have had minimal acceptance in the past for three main groups of practical reasons--pump inefficiency, geometric restraints on lead pipe construction and inability to achieve theoretically attainable automatic pump operation. Inefficiency manifests itself in low pressure output through the lift valve. The lead pipes have had to be constructed with relatively long length and they could not be used under some geographic conditions.
Nonautomatic operation has been the result of the failure of past designs to coordinate opening and closing of the release and lift valves and failure to allow proper volumes of air into the pump housing. In theory, closure of the release valve would generate a pressure increase in the pump housing, which compresses air trapped therein. The lift valve would be constructed with biasing means to open at a predetermined pressure level so that the compressed air would expand and drive water out of the pump. Opening the lift valve would eventually decrease the pump housing pressure. Unfortunately, known ram pump designs have not supplied the proper volumes of air into the pump housing which are necessary to attain an output head under automatic operation. During automatic operation, some air is constantly dissolved into the water, decreasing air volume. When the air volume decreases below a critical level, automatic operation terminates. If an excessive volume of air is supplied into the pump housing, the back pressure will only compress and lift air rather than lift water, which hampers pump efficiency.
If the release valve is constructed so that it automaticaly biases to the open position, the valve will open, allowing more water to flow through the pump body from the reservoir. At least in theory, carefully adjusting the release valve bias force will allow the valve to close once the hydrostatic pressure caused by flowing water through the pump is attained; the release valve then closes, setting up another pressure shock which repeats the lift valve opening process. Unfortunately, it has not been heretofore possible to construct a ram pump having efficient, fully automatic operation.